The present invention relates to a coordinate input device used in a large-scale display system and, more particularly, to a coordinate input device which is used to control an externally connected computer and to write a character, figure, and the like.
As a conventional coordinate input device, a device which senses an image of a beam spot on a screen using a CCD area sensor or linear sensor, and computes and outputs a coordinate value by an image process using a barycentric coordinate position or pattern matching, or the like, a device which uses a position detection element called a PSD (an analog device which can obtain an output voltage corresponding to the spot position), and the like are known.
For example, Japanese Patent Publication No. 7-76902 discloses a device which detects a coordinate position by sensing an image of a beam spot formed by a collimated beam of visible light, and transmitting/receiving control signals by infrared divergent light. Also, Japanese Patent Laid-Open No. 6-274266 discloses a device which detects a coordinate position using a linear CCD sensor and special optical mask.
On the other hand, Japanese Patent No. 2,503,182 discloses the arrangement of a device using a PSD and a correction method of the output coordinate position.
In recent years, a large-screen display tends to have a larger screen size and higher resolution simultaneously with improvement of brightness. For this reason, the resolving power of a coordinate input device must be improved.
Conventionally, as a coordinate input device of this type, a compact, inexpensive device which uses a ring CCD and is resistant against disturbance light, has been proposed. As an input pointing tool, a pen-shaped tool is used. In this case, since the input area is large, a cordless pen improves the operability. In the coordinate input device using the ring CCD, input light from the pointing tool is flickered, and it is detected by the difference between its ON and OFF states. For this reason, the ON/OFF timing of the input light must be detected cordlessly.
However, incoming light often becomes weak due to an insufficient remaining amount of a battery used in the pointing tool, tilt of the pointing tool, or the like. In such case, synchronization with the ON/OFF timing of the input light cannot be attained, and a wrong coordinate value may be detected. When such coordinate value is sent to a host computer connected to the coordinate input device, the cursor position on the monitor of the host computer that indicates the coordinate position suddenly jumps to a point other than the input point, or a line the operator does not intend is input upon using, e.g., a drawing application.
The present invention has been made in consideration of the aforementioned problems, and has as its object to provide a coordinate input device which can accurately input a coordinate position, its control method, and a computer readable memory.
In order to achieve the above object, a coordinate input device according to the present invention comprises the following arrangement. That is, there is provided a coordinate input device for generating a beam spot by irradiating a predetermined position of a coordinate input surface with light coming from a pointing tool, and generating a coordinate value corresponding to the beam spot, comprising:
light-receiving means for receiving the light coming from the pointing tool;
sensing means for sensing the beam spot;
synchronization discrimination means for discriminating if a first signal output from the light-receiving means and a second signal output from the sensing means are synchronized; and
output means for outputting a coordinate value corresponding to the beam spot on the basis of a discrimination result of the synchronization discrimination means.
In order to achieve the above object, a coordinate input device according to the present invention comprises the following arrangement. That is, there is provided a coordinate input device for generating a beam spot by irradiating a predetermined position of a coordinate input surface with light coming from a pointing tool, and generating a coordinate value corresponding to the beam spot, comprising:
light-receiving means for receiving the light coming from the pointing tool;
sensing means for sensing the beam spot;
synchronization discrimination means for discriminating if a first signal output from the light-receiving means and a second signal output from the sensing means are synchronized; and
control means for controlling a clear timing of information sensed by the sensing means on the basis of a discrimination result of the synchronization discrimination means.
In order to achieve the above object, a method of controlling a coordinate input device according to the present invention comprises the following arrangement. That is, there is provided a method of controlling a coordinate input device for generating a beam spot by irradiating a predetermined position of a coordinate input surface with light coming from a pointing tool, and generating a coordinate value corresponding to the beam spot, comprising:
a light-receiving step of receiving the light coming from the pointing tool;
a sensing step of sensing the beam spot using a sensor;
a synchronization discrimination step of discriminating if a first signal output in the light-receiving step and a second signal output from the sensor are synchronized; and
an output step of outputting a coordinate value corresponding to the beam spot on the basis of a discrimination result in the synchronization discrimination step.
In order to achieve the above object, a method of controlling a coordinate input device according to the present invention comprises the following arrangement. That is, there is provided a method of controlling a coordinate input device for generating a beam spot by irradiating a predetermined position of a coordinate input surface with light coming from a pointing tool, and generating a coordinate value corresponding to the beam spot, comprising:
a light-receiving step of receiving the light coming from the pointing tool;
a sensing step of sensing the beam spot using a sensor;
a synchronization discrimination step of discriminating if a first signal output in the light-receiving step and a second signal output from the sensor are synchronized; and
a control step of controlling a clear timing of information sensed by the sensor on the basis of a discrimination result in the synchronization discrimination step.
In order to achieve the above object, a computer readable memory according to the present invention comprises the following arrangement. That is, there is provided a computer readable memory which stores a program code of controlling a coordinate input device for generating a beam spot by irradiating a predetermined position of a coordinate input surface with light coming from a pointing tool, and generating a coordinate value corresponding to the beam spot, comprising:
a program code of a light-receiving step of receiving the light coming from the pointing tool;
a program code of a sensing step of sensing the beam spot using a sensor;
a program code of a synchronization discrimination step of discriminating synchronization between a first signal output in the light-receiving step, and a second signal output from the sensor; and
a program code of an output step of outputting a coordinate value corresponding to the beam spot on the basis of a discrimination result in the synchronization discrimination step.
In order to achieve the above object, a computer readable memory according to the present invention comprises the following arrangement. That is, there is provided a computer readable memory which stores a program code of controlling a coordinate input device for generating a beam spot by irradiating a predetermined position of a coordinate input surface with light coming from a pointing tool, and generating a coordinate value corresponding to the beam spot, comprising:
a program code of a light-receiving step of receiving the light coming from the pointing tool;
a program code of a sensing step of sensing the beam spot using a sensor;
a program code of a synchronization discrimination step of discriminating synchronization between a first signal output in the light-receiving step, and a second signal output form the sensor; and
a program code of a control step of controlling a clear timing of information sensed by the sensor on the basis of a discrimination result in the synchronization discrimination step.